2003 L3130HST cannot disengage front wheels

[Milo Holroyd]

Howdy folks, the tractor has just over 2000hrs. I have had all 4 tires off the ground using the backhoe and front bucket. All 4 tires turn without undue effort or noise. Lever is attached as it should be. All fluids are good (serviced less than 100 hrs ago). I've used the weight of the tractor forward and backward, uphill and down, while steering left and right. Nothing lets the gear slide. could it have twisted a shaft causing it to lock up? The only next step I see is pulling the top off and taking a look. ? appreciate any advice.